Integrated digitizing tablet and color display apparatus and method of operation

ABSTRACT

An integrated digitizing tablet with color display is disclosed. The digitizing tablet portion of the integrated digitizing tablet and display apparatus includes an array of magnetic random access memory (MRAM) cells that can be modified by at least one externally-applied magnetic field, wherein each memory cell has a magnetic bit that changes orientation upon the application of the externally-applied magnetic field to produce an electrical signal based on the orientation of the bit when an electric field is applied across the array. The display portion comprises an array of color pixel cells, each color pixel cell being selected from more than one color type and being coupled to one of the MRAM cells. The MRAM cell is operated to activate the coupled color pixel cell in response to the electrical signal produced by the MRAM cell. Typically, the color pixel cells are selected from the colors red, blue, and green in approximately equal ratios or may be selected from their complementary colors which would include cyan, magenta, and yellow. Any color scheme may be implemented and is not limited to merely three colors or be required to be more than two.

[0001] Two further applications in magnetic random access memory arraysare described in commonly assigned and co-pending U.S. patentapplication No. ______ (HP docket number 10019665-1), entitled “STYLUSBASED INPUT DEVICES UTILIZING A MAGNETIC RANDOM ACCESS MEMORY ARRAY”,and co-pending U.S. application No. (HP docket number 10019666-1),entitled “AN INTEGRATED DIGITIZING TABLET AND DISPLAY APPARATUS ANDMETHOD OF OPERATION”, the disclosures of which are hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention writes generally to digitizing inputdevices and, more particularly, the present invention relates to theutilization of a magnetic random access memory (MRAM) device as adigitizing array within a digitizer apparatus.

[0003] Digitizer systems are well known to those skilled in the art.Typically, an electromagnetic array, or other type of system, isresponsive to a stylus used by a user to enter data directly upon a gridand to control various computer functions by writing, sketching, orpointing the stylus against the digitizer array. Some embodiments locatethe digitizer directly on the monitor; other embodiments separate thetwo devices. Usually, separate digitizers are utilized where a largework surface is needed compared to the size of the display device suchas a monitor screen. Integrated digitizer and display devices areutilized where portability and size are important. As such, varioustypes of computer systems utilize stylus-based technologies and mayinclude portable systems, desktop systems, transportable, orterminal-based systems.

[0004] The integrated digitizer-display systems are integrated only inthe sense that they are coplanar and are fitted together in a commondevice. They are not integrated in that a signal processor is requiredto convert the signals generated by the digitizer into display signalscompatible with the display. Thus, additional circuitry and complexityare involved in even the simplest of digitizer-display systems that areintegrated for direct input on the same display surface where thedigitizer is located.

[0005] Several types of stylus input digitizing devices exist in theprior art. One type involves direct contact of a stylus tip against acapacitive-resistive array. As the stylus tip, such as a metal tip oreven a user's finger, is placed proximate a selected area of adigitizing pad, a capacitive-resistive circuit within the pad detectsthe placement of the stylus and computes its location according towell-known mathematical formulas of a grid-based array. Typically, thecapacitive-resistive array is used over small areas in devices such as aportable digitizer screen or finger-sensitive mouse pad.

[0006] A second prior art system utilizes an electromagnetic digitizerthat interacts with a magnetic-tipped stylus or electromagneticfield-generating stylus in entering data and performing actions desiredby the user. The tip of the stylus interacts with the field on thedigitizer to convey information and data from the user. Typically a gridof intersecting lines produces a field that can be either actively orpassively modified by the field generated by the stylus. Crossing linescan sense the field of the tip to generate a responsive signal, or canproduce a field altered by the stylus during interaction.

[0007] Another embodiment is that of a stylus having an RF transmitterto send signals to the digitizing array, which then detects thetransmitted signals utilizing receiving circuits in the array.Alternatively, the pad locations may be coated and the RF signalgenerated by the stylus interact with the array and are received at areceiver within the stylus itself.

[0008] Further, an alternative embodiment may incorporate a lightsource, such as visible or infrared light placed within the tip of thestylus to reflect off the pad. The stylus uses an imaging device, suchas a CCD camera, to detect optically the return signal, and hence thelocation where the stylus interacts with the digitizer. The system thenprocesses and decodes the received signal and location in order todetermine the appropriate information.

[0009] Each of these systems has had some success; however, each haslimitations that make them difficult or undesirable to use. For example,the direct contact technology is subject to scratches and wear duringnormal operation and has low durability compared to other technologies.

[0010] The wire-grid electromagnetic technology is expensive toimplement and requires many individual wires for greater resolution.Additionally, the electromagnetic digitizers typically require a planarmagnetic material behind the wire-grid sensor to shield the system fromstray magnetic effects. In portable uses, this makes the technology forthe system implementing such technology heavier than necessary. In thelight-based systems, the stylus needs to be corded to the digitizerarray and the need for sophisticated electronics for producing the lightsource as well as the CCD camera must be incorporated and expanded toachieve such a stylus.

[0011] One disadvantage common to all the various types of prior artdigitizing technologies is that the digitizing array must always beunder power in order for interaction of the user's stylus with thedigitizer to be maintained. Further, the user must also save theinformation to long-term storage, such as the hard disk drive on thecomputing system, in order to preserve the content of the user's stylussession. Furthermore, in portable devices, the same can be said that theuser's input must be stored in long-term memory and cannot be maintainedon the digitizer, typically which is overlayed with the displayed systemso that the user can keep the most recent information upon restart ofthe apparatus unless power is provided to preserve the information inmemory.

[0012] Digitizing arrays have been mated with display systems in orderto provide an easy method of drawing and viewing the resultssimultaneously. For example, a digitizing array may be overlayed with anindium tin oxide display panel such that if the user interfaces with thedigitizer using the stylus, the images displayed immediately under thestylus as the user interacts therewith. This enables the user tointeract with the screen as if interacting with real data or writing onan actual writing tablet using a pen. Such technologies always requirethe use of an input signal processor, which coordinates with thedigitizer to receive the user's input via electromagnetic pulses, lightpulses, resistive interaction or the used system to process the signalsfor display on the display apparatus portion.

[0013] Accordingly, what is needed is an improved digitizing apparatusthat has greater resolution than the prior art systems, is easier tomanufacture, and is more durable during actual use. Further, what isrequired is a digitizer apparatus that can be integrated with a displaydevice and that can be manufactured with such a display as anelectroluminescence apparatus using the same processing methods andtechniques.

SUMMARY OF THE INVENTION

[0014] According to the present invention, an integrated digitizingtablet with color display is disclosed. The digitizing tablet portion ofthe integrated digitizing tablet and display apparatus includes an arrayof magnetic random access memory (MRAM) cells that can be modified by atleast one externally-applied magnetic field, wherein each memory cellhas a magnetic bit that changes orientation upon the application of theexternally-applied magnetic field to produce an electrical signal basedon the orientation of the bit when an electric field is applied acrossthe array. The display portion comprises an array of color pixel cells,each color pixel cell being selected from more than one color type andbeing coupled to one of the MRAM cells. The MRAM cell is operated toactivate the coupled color pixel cell in response to the electricalsignal produced by the MRAM cell. Typically, the color pixel cells areselected from the colors red, blue, and green in approximately equalratios or may be selected from their complementary colors which wouldinclude cyan, magenta, and yellow. Any color scheme may be implementedand is not limited to merely three colors or be required to be more thantwo.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Features and advantages of the present invention will becomeapparent to those skilled in the art from the following description withreference to the drawings, in which:

[0016]FIG. 1 illustrates a schematic diagram of a digitizing system withdisplay unit in accordance with the present invention.

[0017]FIG. 2 illustrates a schematic diagram of a stylus interactionleaving a trace on a magnetic random access memory (MRAM) digitizing padof that from FIG. 1;

[0018]FIG. 3 depicts a schematic diagram of an array of MRAM cells ascontrolled by the sense and bit lines.

[0019]FIG. 4 depicts a cross-sectional side view of the stylusinteracting with the digitizer tablet in accordance with the tablet ofFIG. 2.

[0020]FIG. 5 is a diagram of the method steps utilizing inputtinginformation for display within the MRAM digitizer system of the presentinvention.

[0021]FIG. 6 illustrates a schematic diagram of a digitizer overlayed bya display apparatus in accordance with the present invention.

[0022]FIG. 7 depicts a cross-sectional side view of the operation of theMRAM digitizer tablet in accordance with the present invention alongwith a display placed on its surface.

[0023]FIG. 8 illustrates a schematic diagram of the electrical circuitarray utilized in accordance with the present invention where MRAM cellsare provided.

[0024]FIG. 9 illustrates a cross-sectional diagram of a MRAM cellfabricated with an electroluminescence pixel according to a schematicdiagram of FIG. 7;

[0025]FIG. 10 illustrates an alternative embodiment of the MRAM cellinteracting with an electroluminescence pixel where the MRAM cell islocated beneath the pixel.

[0026]FIG. 11 illustrates a schematic diagram of an alternativeembodiment of utilizing an MRAM for activating a pixel in accordancewith the present invention.

[0027]FIG. 12 illustrates a schematic diagram of an alternativeembodiment of a memory cell implemented to activate a pixel inaccordance with the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0028] For simplicity and illustrative purposes, the principles of thepresent invention are described by referring mainly to exemplaryembodiments thereof. However, one of ordinary skill in the art wouldreadily recognize that the same principles are equally applicable tomany types of digitizer systems with displays.

[0029] A digitizing apparatus that connects to a display system inaccordance with the present invention is illustrated in FIG. 1. Adigitizer 100 is disclosed that utilizes an array of magnetic randomaccess memory (MRAM) cells to function as a stylus-based input device.Digitizer 100 couples to a signal processor 102, which further connectsto a display system 104. Signal processor 102 receives signals from thedigitizer 100 and processes them for display on video display 104.Digitizer 100 further includes control logic 105 that is utilized tocontrol digitizer 100 during operations such as array read, array write,and array clear, which are well known to those skilled in the art.

[0030] Digitizer 100 is shown in further detail in FIG. 2, whichillustrates a trace of a stylus tip over the surface of digitizer 100.The digitizer 100 is composed of an array of memory cells 106. Eachmemory cell has at least two state possibilities based on theorientation of a magnetic bit found within the cell 108. As a trace of astylus interacting with the surface of digitizer 100 occurs, the bitwithin the cell is reoriented causing the state of memory cell(s) 106 tochange as shown in cell 108. The trace 110 illustrates a path taken bythe stylus. An electrical signal is then applied to the array of cells106 as a read signal to generate a read output of those cells modifiedby the bit change. The read output signal, which is a modified electricsignal caused by the changed bit positions, is then sent to the signalprocessor 102 of FIG. 1 where it is processed according to the patterntraced by the user. The trace 110 is then displayed on display unit 104.

[0031] MRAM cells have emerged as an alternative to long-term storageand the MRAM cells have similar properties of fast access ofsemiconductor memory. They can serve as long-term storage devices sincethey have the ability to store information indefinitely. An MRAM cellstores a bit of information based on the magnetic orientation ofmagnetization placed in a patterned thin-film magnetic element. Thismagnetic film is designed so that it has two stable and distinctmagnetic states. The stable magnetic states define a binary one (1) or abinary zero (0). Although the digital information is stored in a thinmagnetic film, many layers of very carefully controlled magnetic anddielectric layers are associated with a memory element.

[0032] One example of an MRAM cell utilizes spin-tunneling effects andis known as a spin-tunneling device. FIG. 3 illustrates a schematicdiagram of such an MRAM cell 106. MRAM cell 106 includes a tunnelingbarrier layer 300, a data storage or sense layer 302, and a referencefilm or pinned layer 304. The pinned layer 304 has a magneticorientation that is fixed so as not to rotate in the presence of anapplied magnetic field in the range of interest. The sense layer 302 hasa magnetic orientation that is variable between a state aligned with thestate of the pinned layer 304 and a state in misalignment with the stateof the pinned layer 304. These orientations correspond to a lowresistance state and a high resistance state, respectively. Aninsulating tunnel barrier layer 300 sandwiches between the magneticpinned layer 304 and the magnetic sense layer 302. The insulating tunnelbarrier layer 300 allows quantum mechanical tunneling to occur betweenthe sense layer 302 and the pinned layer 304. The tunneling iselectron-spin dependent, causing the resistance of the memory cell tovary as a function of the relative orientations of the magnetizations ofthe sense layer and the pinned layer.

[0033] The magnetic state of a selected memory cell 106 may be changedby applying currents to a word line 308 and a bit line 310 crossing theselected memory cell 106. The currents produce two orthogonal magneticfields that, when combined, will switch the magnetic orientation of theselected memory cell 100 between the aligned and misaligned states, alsoknown as the parallel and anti-parallel states, respectively. Otherunselected memory cells receive only a magnetic field from either theword line or the bit line crossing the unselected memory cells. Thesingle field is not strong enough to change the magnetic orientation ofthe unselected cells, so they retain their magnetic orientation. When astylus having a magnetic tip is placed proximate the cells, a sufficientfield is then applied to cause the magnetic state of the cell to change.This results in a change of orientation between the parallel and theanti-parallel states.

[0034] One advantage of utilizing MRAM cells other that of the prior artis that MRAM cells hold their orientation indefinitely without anyexternal force applied to them. This means that no electric field orelectric current must be applied to the MRAM cell in order to maintainthe magnetization orientation of its magnetic bit. Thus, should thedevice be turned off, the orientation last impressed upon the cell willbe maintained indefinitely. Once the system is reenergized, a readoutoperation would signal that the state has been maintained and thus anorientation is preserved. This allows a signal to be sent that wouldsignify to the signal processor and therefore displayed on the displaydevice the previous drawing made by the user on the digitizer arraybefore the power was turned off.

[0035] The system utilizes a stylus with a magnetic tip in oneembodiment that can be scanned over the digitizer array. Beneath thesurface of the pad lies an array of MRAM cells very similar to the MRAMarchitecture previously described. As the stylus moves, a magnetic fieldis generated by the magnet within the tip of the stylus to cause bits toflip in the path of the stylus movement and leaves a trace as shown inFIG. 2. The MRAM array is continuously read and scanned for changes inthe bit patterns recorded in it. As the stylus moves across the array,the trace changes the pattern and its path is displayed on the display.

[0036] In one embodiment, the stylus tip shown in FIG. 4 comprises apermanent magnet that produces a known field. The magnet may be placedin the tip used to interact with the tablet or the stylus may be coatedwith a magnetic material that generates a magnetic field that can affectthe MRAM memory cells. Supporting drive electronics are found within thedigitizer and are well known to those skilled in the art. Initially, thedrive electronics set all bits in the array of memory cells in a firstdirection. As the stylus tip moves across the array, the magnetic fieldinduces a bit change in a direction opposite of their originalalignment. The drive electronics periodically may reset all bits totheir original orientation or when directed to by the user.

[0037] In an alternative embodiment, the tip of stylus 112 may produce avarying magnetic field using a current carrying coil. Since the currentmay be altered by changing its direction and its strength, the affectedbits within the memory cells will be placed in a unique pattern as theyhave been changed both in space and in time in response to the currentpattern selected by the user with the stylus. The current pattern may bevaried by the user pressing the tip downward against the array, whichmay signify a button-press operation such as that on a mouse-typepointing device, or selecting one or more buttons on the stylus, whichmay signify different key clicks such as those in a mouse being a right,left, or middle button selection. In yet another embodiment, the varyingcurrent pattern may also signify changing colors, which will bedescribed in greater detail below.

[0038] Additionally, since the MRAM cells operate independently of theother cells and the stylus, more than one stylus may also be utilized.Accordingly, a plurality of stylus may be utilized, each operatingindependently of the other as the cells they affect also operateindependently of one another. Thus, the use of one stylus as illustratedis but exemplary of the invention and not limiting. For example, amulti-fingered input system may be implemented. The multi-fingered inputdevice may be implemented within a glove array wherein each finger has adistinctly coded stylus to generate a select signal unique from theother signals. The multi-fingered input system would enable one user toproduce multiple traces on the underlying MRAM sensor array inaccordance with the present invention.

[0039] The magnetic cell array is sensitive to magnetic fields. Thestrength of the magnetic field produced by the stylus is selected to besufficient enough to be detected by the array without direct contact.This allows a covering to be placed on the top surface of MRAM cellssuch that the pad may be written upon directly without fear ofscratching or damaging the screen or array surface below.

[0040]FIG. 5 illustrates a flow diagram of a method that utilizes thearray of MRAM cells as a digitizer device in accordance with the presentinvention. Initially, as shown in block 500, an array of such memorycells is formed. The memory cell includes additional control logic toidentify particular locations on the digitizer panel where the stylusinteracts. The detection of the stylus interaction of changing the bitorientation within selected cells enables a signal to be sent to asignal processing unit, which then causes the trace to be displayed on adisplay apparatus in accordance with the present invention. Once theMRAM cell array has been obtained, the user then applies a magneticfield to the cells within the array, as shown in block 502, via a stylusin order to generate a trace line on the display.

[0041] Next, the system applies a read electric signal to the array,shown in block 504, in order to determine which memory cells the userhas altered via the stylus application. This electric signal, asmodified by the affected cells, is forwarded to the signal processorwhere it is processed so as to identify those cells that have beenmodified. Once the cells are identified, pixels on the screen thatcorrespond to the cell location on the digitizer are then activated toreproduce the trace on the display. During the interaction of the styluswith the digitizer panel, the system determines if the user hasperformed a particular action as shown in block 506. If the user ismerely applying a magnetic field to the MRAM array, then the system asshown on block 508, reads the output signal from each signal. Otherwise,if the system detects that the user has performed a desired action, thesystem, as shown in block 510, performs the action requested by theuser. Typically, these actions are similar to the action the user maytake with a pointing device such as a mouse or roller ball. The actionscan include a right or left mouse click or a center mouse click. Theexecution of a program or opening of a web page can also be convenientlylocated within an operating range of the stylus as implemented by theuser.

[0042] Lastly, once the array has had its electric signal applied to itand the output signals have been read from each cell, the signalprocessor, as shown in block 512, processes the output electric signalsand displays an image on the display corresponding to the image datadiscerned from the output electric signal. It should be noted that theoutput electric signal can provide output for more than one traceperformed on the digitizer at any time as well as that different colorsmay be used for different traces or stylus actions as contemplatedwithin the invention.

[0043] An alternative embodiment of the present invention is illustratedin FIG. 6. A display panel 104 physically mated with a digitizing MRAMarray 100 is illustrated in the schematic diagram of FIG. 6. Display 104is placed over digitizer 100 such that as the user traces the stylusacross the surface of display 104, the magnetic field interacts with thearray 100 below and causes a trace to be drawn exactly where the stylusinteracts with the display panel. Signals are sent to the signalprocessor 102 and then sent to the display panel 104 for display. Thishas the advantage of integrating a digitizing apparatus 100 with adisplay apparatus 104 such as are utilized on laptop computers andpersonal digital assistances (PDA) devices and the like.

[0044] Another embodiment of the invention, as illustrated in FIG. 7,mates a display apparatus 104 with a digitizer apparatus 100 such thatthe digitizer, utilizing the MRAM cells, actively controls the displaypixels found within a display panel 104. The display panel used in thistype of system typically utilizes transistors such as in an activematrix and is well known to those skilled in the art. The MRAM cells inthe array are mated with a selected transistor to activate the pixelwithin the display in accordance with the present invention.

[0045]FIG. 8 illustrates a schematic diagram of an array of pixels ascontrolled by a memory cell as integrated in a single digitizer-displaysystem 200. Each pixel 202 is represented in the contents located withinthe dotted block and also contains a pixel enable line 206, a first rowmemory cell voltage line 208, and a second row memory cell voltage line210.

[0046] Each display pixel 202 includes an MRAM cell 212, fixed betweenthe two row memory cell voltage lines 208 and 210. Voltage cell line 210is then further coupled to a switching device 214, such as a fieldeffect transistor, which has its source coupled to the pixel enable line206. Transistor 214 controls a pixel diode 216. In this illustration,pixel diode 216 generates a light of red color with a series of red,green, and blue pigments being provided in adjacent pixels to provide acolor display and to depict an implementation of an MRAM array digitizercontrolling a color apparatus and providing distinct color selectionthrough the use the stylus. Each pixel 216 is coupled to a capacitor218, to provide a constant power source to the pixel 216 when it isactive.

[0047] The array 200 of FIG. 8 illustrates three pixels, selected fromred, green, and blue (RGB). The array actually comprises a plurality ofthe pixels, with three colors being grouped together in individual cellscomprising a single color pixel and a single MRAM. Thus, the arraycomprises a plurality of color pixels formed in an RGB matrix. Althoughthere is illustrated an equal number pixels for each color, it should benoted that it is intended that the intensity level of each color begenerally equal. As such, the designer will add additional pixels of onecolor over another in order to achieve equal color intensity. Or, theintensity of each color pixel can be controlled by another memory cellso that only one pixel per color is planned.

[0048] The array can comprise anywhere from just a few pixels in the Xand Y directions to as large as is necessary to supply a displayapparatus of conventional size. Such a display would have over athousand lines in both the X and the Y dimensions.

[0049]FIG. 9 illustrates a cross-sectional view of a cell 202 asimplemented in a semiconductor material. The MRAM cell 212 is fabricatedin the semiconductor material adjacent a light emitting pixel 216. Theswitch 214, which includes a source connection 218 and a drainconnection 220, connects to pixel 216 for activation. A gate 222 isformed below the MRAM cell 216. The cell also includes proper isolationand conductive layers necessary for patterning and manufacturing an MRAMcell as well as a display pixel.

[0050]FIG. 9 further illustrates that the control cell portion is placedadjacent the display cell 216. The magnetic switching cells aretypically much smaller than the display pixels. As such, the MRAM cellscan be fabricated adjacent the display pixels since the display pixelsare generally at least one order of magnitude larger than the MRAMcells. For example, the MRAM cells have a form factor ranging from 0.2to 2.0 microns while the display pixels have a form factor of at 4 or 5microns or larger. As such, additional control switches may be utilizedbecause of their size and can serve as brightness control, among otherneeds.

[0051] Placing the memory cell adjacent the pixel uses moresemiconductor surface area than placing the memory cell below the pixel.Thus, an alternative embodiment of locating the memory cell 212 belowthe pixel display cell 216 is shown in FIG. 10. This enables greaterresolution and greater density to be achieved in the same surface areaas that of the pixel array shown in FIG. 9. The memory cells aredisplaced but a small distance behind or below the pixels. The distanceis slight enough that the stylus can still interact with the memorycells when moved across the top surface of the digitizing display. Thisincreased pixel density is not possible using other technologies thatplace the switch within the same substrate as the pixel. Thisdisplacement also makes the magnetic cells less susceptible to outsidemagnetic fields, which will typically attenuate before affecting theorientation of the bit within a given memory cell.

[0052]FIG. 11 illustrates yet an alternative embodiment of a directlyactivated display pixel 216, as contemplated in the present inventionwherein memory cell 212 controls the source of the switching transmitter214 as opposed to being connected directly to the gate as wasillustrated in FIG. 8. The array includes a first column memory voltagecontrol line 232 and a second column memory voltage line 234, whichconnect in parallel with memory cell 212. A pixel row control line 236couples to the gate of transistor 214. When a signal is applied tovoltage line 232, a current flows through memory cell 212 depending uponthe orientation of the bit therein. If the orientation allows forcurrent flow through the cell, then switch 214, activated by controlline 236, causes pixel 216 to activate and display. Additional cells areprovided to form an array of cells as contemplated in the presentinvention.

[0053]FIG. 12 illustrates yet another alternative embodiment thatutilizes a memory cell 212 in an improved circuit for controlling theactivation of a display pixel 216. A pair of memory cells 212 controlsthe activation of switching transistor 214. The pair of memory cells 212is placed within a differential sense amplifier circuit to determine thesignal strength of either an activated or non-activated memory cellusing conventional means. A first cell 212 receives a first signal andthe second cell receives a second signal complementary to the firstsignal. The use of complementary cells is exemplary only and is utilizedas it improves the signal-to-noise ratio of the sensing electronics.Alternatively, a single cell can be utilized that is not dependent on acomplementary cell for improved noise reduction or accuracy.

[0054] Further, the cell size is scalable depending upon the accuracydesired as well as the display device integrated within the digitizingsystem. For example, current processing techniques yield cell sizesranging from 0.1 micron to 0.3 micron in memory array applications. Forapplications in display and digitizer systems, cell sizes comparablewith the display pixel and switching circuit sizes is acceptable, whichprovides sizes in the micron to the tens of microns size. Thisscalability provides yet another advantage over that of the prior art.

[0055] Thus, it has been demonstrated that a digitizing device utilizingan array of MRAM cells may be incorporated to interact with a displaydevice and that the digitizer device may actually be combined with thedisplay using thin-film transistor cells so the memory cells directlyactivate the pixels within an active matrix display. The result is adigitizer-display that needs little, if any, signal processing logic asis required in other digitizer-display units. Thus, as the user writes atrace directly on the display, the trace is displayed directly on thescreen with little, if any, intermediary processing.

[0056] Further, since the MRAM cells array serves as an addressablememory array, this simplifies the drive electronics typically requiredin prior art systems. Additionally, the displayed image/graphics orotherwise defined information can be stored in a non-volatile fashiondue to the nature of the MRAM cells as previously described. Since theMRAM cells retain the last selected orientation of the memory bitsindefinitely, when the display system is turned off and then turned onagain, no loss of information occurs. The display acts as a writable andreusable paper medium rather than as a conventional digitizer tabletthat always required saving of data to a long-term memory store ratherthan directly within the digitizer itself.

[0057] Although thin-film transistor (TFT) cells have been depicted inthe specific embodiments of the present invention, alternative displaycells may also be utilized. In addition, the MRAM cell disclosed hasutilized tunneling magneto-resistive (TMR) effect, but other MRAM cellsmay also be contemplated. These will include cells based onmagneto-resistive (MR) effect, giant magneto-resistive (GMR) effect,magnetic tunneling junction (MTJ) effect, or colossal magneto-resistive(CMR) effect.

[0058] There are four very different physical effects that produce MR ofdifferent types: AMR (anisotropic), GMR (giant), TMR (tunneling) and CMR(colossal). Tunneling Magneto-resistance (TMR) or the tunnelingmagneto-resistive effect (TMR effect) is the change in resistancegenerated by the physical effect of spin-dependent tunneling (SDT) thatis seen in a magnetic tunnel junction (MTJ, also sometimes called an SDTjunction).

[0059] For illustration, an MTJ-based cell behaves as a resistance withtwo states, having a high resistance state and a low resistance state.The memory cell is connected to the gate of the transistor switch 216and the memory cell resistance is chosen such that the drive voltagewill turn on or off the pixel or the switch 214 depending upon the stateof the memory cell 212. Once the switch 214 turns on (or off) it causesthe neumatic liquid crystal display to block (or pass) light through it.The state of the cell 212 is changed externally by the presence of thestylus in the magnetic field located within the tip of the stylus. Thisfurther causes the switch 214 to turn off or on and consequently thepixel turns off or on.

[0060] Additionally, switching and conveying electronics is alsoincorporated into the design such that the entire memory cell array maybe refreshed or erased or individual cells may be turned on or off orrefreshed. Further, the electronics allows for the information in thecells to be stored in the long-term memory device should the contents inthe array need to be saved but also erased so that additional writingsmay be performed.

[0061] The application of color to the memory cell array can be obtainedby creating memory cells of differing levels of sensitivity. This meansthat the cells for red may be sensitive to a neumatic field of aparticular field strength separate from that of the blue or green pixelsand vice versa. This allows the user the option of modifying colors onthe fly by actively selecting the level of field strength desired thatwould activate one, two or all three pixels at any time to achieve thedesired colored results.

[0062] It is to be understood that the above-described arrangements areonly illustrative of the application for the principles of the presentinvention. Numerous modifications and alternative arrangements may bedevised by those skilled in the art without departing from the spiritand scope of the present invention and the appended claims are intendedto cover such modifications and arrangements. Thus, while the presentinvention has been shown in the drawings and fully described above withparticularity and detail in connection with what is presently deemed tobe the most practical and preferred embodiment(s) of the invention, itwill be apparent to those of ordinary skill in the art that numerousmodifications, including, but not limited to, variations in size,materials, shape, form, function and manner of operation, assembly anduse may be made, without departing from the principles and concepts ofthe invention as set forth in the claims.

1. An integrated digitizing tablet and display comprising: a digitizingtablet comprised of an array of magnetic random access memory (MRAM)cells that may be modified by at least one externally-applied magneticfield, each memory cell having a magnetic bit that changes orientationupon application of the externally-applied magnetic field to produce anelectrical signal based on the orientation of the bit when an electricfield is applied across the array; and a display comprised of an arrayof color pixels, each color pixel selected from more than one color typeand being coupled to one of the MRAM cells, which activates the coupledcolor pixel in response to the electrical signal produced by the MRAMcell.
 2. The invention as claimed in claim 1 wherein each color pixel isselected from either red pixels, blue pixels, and green pixels, inapproximately equal ratios.
 3. The invention as claimed in claim 1wherein the magnetic field is a fixed field.
 4. The invention as claimedin claim 1 wherein the magnetic field can vary during interaction with aMRAM cell.
 5. The invention as claimed in claim 1 further comprising astylus that has a first tip that generates the externally-appliedmagnetic field.
 6. The invention as claimed in claim 1 wherein a secondexternally-applied magnetic field can interact with the MRAM cell arraysimultaneously with the at least one externally-applied magnetic field.7. The invention as claimed in claim 5 wherein the stylus can interactwith the digitizer tablet to indicate an action to be performed.
 8. Theinvention as claimed in claim 5 wherein the stylus included acurrent-carrying coil to interact with the MRAM cell array.
 9. Theinvention as claimed in claim 1 wherein the array of color pixels areformed of TFT display cells and are placed over the MRAM cell array. 10.A method of converting user input into image data, comprising: providingan integrated array of magnetic random access memory cells and colorpixels, each MRAM cell having a magnetic bit that changes orientationupon application of a magnetic field and each cell being further coupledto one color pixel to activate the pixel; applying a magnetic field tothe array to change the magnetic bit orientation of at least a portionof the MRAM cells; applying an input electric signal to the array;activating the color pixels coupled to the affected MRAM cells todisplay an image.
 11. A method of converting user input into image dataaccording to claim 10 wherein the color pixels form an array consistentwith the array of MRAM cells and wherein the color pixels serve as avideo display directly controlled by the array of MRAM cells.
 12. Amethod of converting user input into image data according to claim 10also comprising applying a second magnetic field, independent of thefirst magnetic field, to change the magnetic bit orientation of at leasta second portion of the MRAM cells.
 13. A method of converting userinput into image data according to claim 10 wherein the magnetic fieldapplying step further comprises selectively varying the magnetic fieldduring application to affect the magnetic bit orientation of the atleast a portion of MRAM cells.
 14. A method of converting user inputinto image data according to claim 10 also comprising: sensing an actionperformed by a user; and performing a function associated with thesensed action.
 15. A method of converting user input into image dataaccording to claim 10 wherein the magnetic bit orientation for each cellis maintained without refresh.
 16. A method of converting user inputinto image data according to claim 11 further comprising mating adisplay device to the MRAM array wherein the displayed image correspondsto the location proximate where the magnetic field is applied to theMRAM array.
 17. A method of converting user input into image dataaccording to claim 11 further comprising, in the event of an electricalpower stoppage to a display device and the MRAM array, redisplaying theimage based on the magnetic bit orientation of the MRAM cells within theMRAM array upon return of electrical power.
 18. An integrated digitizingand display cell comprising: a magnetic random access memory (MRAM) cellthat may be modified by at least one externally-applied magnetic fieldand having a magnetic bit that changes orientation upon application ofthe externally-applied magnetic field to produce an electrical signalbased on the orientation of the bit when a read signal is applied acrossthe MRAM cell; and a color pixel selected from more than one color typeand being coupled to the MRAM cell, which activates the color pixel inresponse to the electrical signal produced by the MRAM cell.
 19. Theinvention as claimed in claim 18 wherein the digitizing and display cellhas a form factor of less than one micron.
 20. The invention as claimedin claim 18 wherein the magnetic field is a fixed field.
 21. Theinvention as claimed in claim 18 wherein the magnetic field can varyduring interaction with a MRAM cell.
 22. The invention as claimed inclaim 18 further comprising a stylus that has a first tip that generatesthe externally applied magnetic field.
 23. The invention as claimed inclaim 22 wherein the stylus can interact with the MRAM cell to indicatean action to be performed.
 24. the invention as claimed in claim 18wherein the pixel is a TFT display pixel.
 25. The invention as claimedin claim 18 wherein the pixel is selected from the color type red,green, or blue.
 26. The invention as claimed in claim 18 wherein thepixel is selected from the color type cyan, magenta, or yellow.